JP4827452B2 - Method for producing lead-acid battery - Google Patents

Description

  The present invention relates to a method for producing a lead storage battery, particularly a control valve type lead storage battery.

Control valve-type lead-acid batteries are manufactured by battery formation in which an unformed electrode plate is housed in a battery case, and electrodes obtained by immediate chemical conversion in which a plate is formed in a dedicated conversion tank. In some cases, the plate is housed in the battery case and then charged for the first time.
When using electrode plates obtained by immediate chemical conversion, the positive and negative electrode plates can be individually formed and sufficient chemical conversion can be performed, and the method used because the amount of electrolyte to be injected into the storage battery can be easily adjusted It is.

On the other hand, control valve type lead used for standby use such as uninterruptible power supply system (hereinafter referred to as UPS) (how to use it for emergency use when commercial power supply fails) The storage battery is always in a state of being float-charged with a constant voltage in order to compensate for the self-discharge of the storage battery and keep the battery fully charged at all times. The life of a control valve type lead-acid battery when it is float-charged for standby use is generally reduced in conductivity due to corrosion of the positive electrode current collector grid, reduced adhesion between the active material and current collector grid due to corrosion expansion, The main cause is an increase in internal resistance due to a decrease in electrolyte due to moisture permeation.

Float charging is carried out to compensate for self-discharge. However, since a current exceeding the self-discharge amount flows in the lead storage battery, corrosion and water decomposition of the positive electrode current collection grid are promoted, and the generated oxygen gas As the amount increases, the battery temperature rises due to the recombination reaction at the negative electrode, resulting in a vicious circle in which the float current further increases. It will have a serious adverse effect on battery life.

  In the control valve type lead-acid battery, most of the oxygen generated from the positive electrode during charging including float charging is absorbed by the negative electrode to become lead oxide. Thereafter, lead oxide reacts with sulfuric acid, which is an electrolytic solution, and changes to lead sulfate. This lead sulfate is charged and returns to lead. Therefore, when the amount of oxygen generated from the positive electrode is large and the amount absorbed by the negative electrode plate is increased, a large amount of float current flows to reduce lead sulfate.

In order to reduce the float current and improve the life characteristics, control of the negative electrode pore volume (Patent Document 1), addition of lignin with a limited functional group to the negative electrode active material (Patent Document 2), and the like have been implemented. . The purpose of these is to increase the negative electrode overvoltage during charging, thereby reducing the positive electrode overvoltage and suppressing the generation of oxygen from the positive electrode, reducing oxygen absorption into the negative electrode and suppressing the float current.
JP 09-199115 A JP 2002-117856 JP

In recent years, control valve-type lead-acid batteries for standby use such as UPS have a long life requirement of 10 years or more in a 25 ° C. environment, and further improvements are desired. In addition to the above-mentioned patent documents, an increase in the amount of lead in the positive electrode current collector grid taking into account the weight loss due to corrosion has been implemented in order to improve the life characteristics, but this is not preferable from the viewpoint of energy density.

In order to achieve the long life of 10 years or more required for UPS or the like while maintaining the lead amount of the positive electrode current collecting grid low, it is necessary to further reduce the float current.

In order to solve the above-described problems, at least a step of initial discharge and initial charge after injection and a step of charge and discharge for subsequent activation for a storage battery assembled using positively and negatively electrode plates formed immediately Provided is a method in which any one of the steps is performed at an ambient temperature of 40 ° C. or higher, and in either case, the depth of discharge is 50% or higher.

(Function)
According to the method of the present invention, the first discharge and the first charge or the subsequent activation charge / discharge are performed at a high temperature, and by increasing the depth of discharge, dissolution of lead sulfate as a discharge product at the negative electrode is performed. The amount and the amount of diffusion increase. Moreover, the surface area of the metallic lead, which is the negative electrode active material, is reduced by charging at the same temperature after discharging. This degree becomes more conspicuous as the battery temperature is higher or the discharge depth is deeper.

Since the negative electrode overvoltage at the time of float charge increases by reducing the surface area of the negative electrode active material, the float current can be reduced.

The initial charge is the first charge after discharge, and is intended to charge against discharge and to charge a very small amount of unformed part in the electrode plate generated in the chemical conversion process.

Activation charging / discharging is charging / discharging applied for the purpose of obtaining further stabilization and improvement of battery characteristics after discharging and initial charging.

In the present invention, the depth of discharge is set to 50% or more. However, in low rate discharge, if the depth of discharge exceeds 98%, the risk of negative electrode dendrite generation due to the rapid increase in the solubility of lead sulfate increases. A range of 80% is desirable.

Charging is also performed for the purpose of ensuring adhesion at the lattice interface after the injection.

  As described above, according to the present invention, the discharge temperature after injection of the lead-acid battery, the initial charge, or the subsequent activation charge / discharge, the ambient temperature is 40 ° C. or higher and the discharge depth is 50% or higher. As a result, the crystal growth of the negative electrode active material is promoted, the specific surface area of the negative electrode is reduced, and the negative electrode overvoltage is increased during charging. Therefore, the overvoltage of the positive electrode is reduced, the generation of oxygen is suppressed, and the float current is reduced. The effect is obtained.

For this reason, the thermal escape of the battery can be prevented, the positive electrode corrosion is also suppressed, and there is an effect that the life of the lead storage battery used for a long time in UPS or the like can be extended.

Hereinafter, embodiments of the present invention will be described.

Immediately formed positive and negative plates were alternately laminated through separators, assembled and stored in a predetermined battery case, and a prescribed amount of liquid was injected to produce a control valve type lead-acid battery. The lead storage battery is heated with warm water or warm air to be discharged and initially charged, and further, charge / discharge for activation is performed. Furthermore, at that time, during discharge, the depth of discharge exceeds a certain amount.

Thereafter, each battery was float charged at an ambient temperature of 60 ° C. and a voltage of 13.65 V, and the float current was measured after one week. Each battery was disassembled and the specific surface area of the negative electrode active material was measured by the BET method.

Next, in order to confirm the battery life improvement effect, in order to promote the deterioration of a part of the battery as a life test, float charge was performed at an ambient temperature of 60 ° C. and a voltage of 13.65 V, and after 6 months, a capacity test and a measurement of the positive electrode grid corrosion were performed. It was. The capacity test conditions were an ambient temperature of 25 ° C. and a final voltage of 10.2 V. The discharge time at a discharge current of 1.75 A (0.25 CA) was measured and carried out every month. The amount of corrosion was determined by removing the corroded material from the positive electrode grid sample after the life test with an alkaline mannitol solution and measuring the reduced weight.

The positive and negative plates formed immediately by forming the electrode plates in the chemical conversion tank are assembled in advance through a liquid retaining separator (retainer mat), and the electrode plate group is divided into six parts by partition walls. A control valve with a capacity of 12 V and a capacity of 7 Ah is prepared by pouring a specified amount so that the electrode plate group is impregnated with an electrolytic solution composed of an aqueous sulfuric acid solution after being accommodated in each cell chamber having six cell chambers. A lead acid battery was prepared. This lead-acid battery is held in a constant temperature bath at each ambient temperature of 25 ° C., 35 ° C., 40 ° C., and 50 ° C., and the discharge is performed at a constant current of 0.7 A and the discharge time is 3 hours and 4 hours. The discharge depth was set to 5%, 7.5 hours, and 10 hours under the conditions of 30%, 40%, 50%, 75%, and 100%, respectively. Similarly, the initial charging condition was a constant current of 0.7 A, and the charging time was 13 hours, 14 hours, 15 hours, 17.5 hours, and 20 hours.

After that, each lead storage battery was float-charged for 1 week at an ambient temperature of 60 ° C. with a constant voltage of 13.65 V, and the float current after 1 week and the specific surface area of the negative electrode active material after disassembly were measured. 1 is shown.

As apparent from Table 1, Examples A to C and 1 to 6 of the present invention in which the ambient temperature was 40 ° C. or higher had a 60 ° C. float charging current reduced as compared with Comparative Examples 1 to 10. Furthermore, the specific surface area of the negative electrode active material is reduced. In particular, Examples 1 to 6 in which the depth of discharge at the time of discharge is 50% or more are excellent because both the float current and the negative electrode specific surface area are further reduced.

This is considered to be because the negative electrode active material crystal grew larger when the Example was reduced from lead sulfate to lead during the initial charge because the storage battery temperature was higher. In the examples, since the negative electrode specific surface area is small, the negative electrode overvoltage during charging increases, the positive electrode overvoltage decreases, oxygen generation decreases, and therefore, the oxygen absorption of the negative electrode decreases and the float current also decreases. It is done. Since Examples 1 to 6 having a depth of discharge of 50% or more have a deeper seismic intensity than Examples A to C , the amount of lead sulfate reduced from lead sulfate to that extent is increased, and the amount of negative electrode active material that has grown greatly And the negative electrode specific surface area tends to decrease. Therefore, it is considered that the float current and the negative electrode specific surface area were further reduced by setting the ambient temperature to 40 ° C. or higher and the discharge depth to 50% or higher.

In the above embodiment, the discharge current is 0.1 CA (0.7 Ah). However, the present invention is not limited to this, and a larger or smaller current may be used.

Further, in both the comparative example and the example, the immediate discharge end voltage when the discharge depth is 100% is equal to or lower than the target end voltage of 10.5 V at 0.1 CA discharge. In this case, the battery is in an overdischarged state, the lead oxide of the negative electrode reacts with sulfuric acid to become excess lead sulfate, and the sulfuric acid specific gravity of the liquid is abnormally lowered to increase the solubility of lead sulfate. For this reason, the danger that a dendrite will generate | occur | produce from an active material at the time of charge after that and will cause a short circuit of an electrode plate increases. Therefore, it is considered that the depth of discharge is 80% or less.

Next, in order to confirm the effect of improving the long-term life of the battery, the batteries of Examples 1 and 4 and Comparative Example 3 were further subjected to a life test at an ambient temperature of 60 ° C. for 6 months. The condition at this time is that the charging voltage is fixed at 13.65V, and after 6 months, the charging time is 25 ° C, the discharge current is 0.25CA, the duration until the discharge end voltage is 10.2V, and the capacity is The positive electrode lattice corrosion amount after the test was measured. The results are shown in Table 2. It can be confirmed that each of the examples has a longer duration than the comparative example, and the corrosion of the positive grid is also suppressed.

A control valve type lead-acid battery having a capacity of 12 V and a capacity of 7 Ah produced in the same manner as in Example 1 was discharged at room temperature at a current of 1.5 A for 2 hours, and then charged at a current of 0.7 A for 14 hours. Thereafter, the lead storage battery was discharged at a constant current of 0.7 A while maintaining the ambient temperature at 25, 35, 40, and 50 ° C. in a thermostat. The discharge time was 3 hours, 4 hours, 5 hours, 7.5 hours, and 10 hours, and the discharge depth of each battery was 30%, 40%, 50%, 75%, and 100%. Next, the battery was charged and discharged at the same current of 0.7 A so that the charge amount was 120% of the discharge amount.

Table 3 shows the results of measuring the float current after charging for 1 week at an ambient temperature of 60 ° C. and a voltage of 13.65 V for each battery, and the specific surface area of the negative electrode active material after disassembly.

In Examples E to H and 7 to 12 of the present invention, the charge current at 60 ° C. is reduced as compared with Comparative Examples 11 to 20, and the specific surface area of the negative electrode active material is reduced. In particular, Examples 7 to 12 when the depth of discharge at the time of discharge is 50% or more are excellent because both the float current and the negative electrode specific surface area are further reduced.

Next, in order to confirm the effect of improving the long-term life of the battery, the batteries of Examples 7 and 10 and Comparative Example 13 were subjected to a life test at an ambient temperature of 60 ° C. for 6 months. The amount was measured. The results are shown in Table 4. In all of the examples, the decrease in the battery capacity is small compared to the comparative example, and it can be confirmed that the corrosion of the positive electrode grid is suppressed.

In each of the above-described embodiments, an example in which heating is performed at 40 ° C. or higher at the time of discharge and initial charge or activation charge / discharge is shown. Obtained.

Claims (2)

  In a method for producing a lead-acid battery assembled using positively and negatively electrode plates prepared immediately, at least one of the steps of discharging and initial charging after injecting an electrolytic solution, or the subsequent activation charging / discharging step Is carried out at an ambient temperature of 40 ° C. or higher. The method for producing a lead-acid battery according to claim 1, wherein the depth of discharge is 50% or more.